Lubricating composition containing surface-esterified siliceous solid and organophilic clay



United States Patent LUBRICA'IING COMPOSITION CONTAINING SUR-FACE-ESTERIFIED SILICEOUS SOLID AND OR- GANOPHILIC CLAY Jacques L.Zakin, Flushing, N. Y., assignor to Socony Mobil Oil Company, Inc., acorporation of New York Application January 17, 1955 Serial No. 482,383

No Drawing.

9 Claims.

inorganic gelling agents.

Lubricating greases may be considered as thickened oils. Variousmaterials have been employed in the past to effect the desiredthickening. Thus, it has been common practice to employ metal soaps offatty acids, such as metal stearates or metal oleates, as thickening orgelling agents. In recent years, a variety of inorganic greasethickening agents have been used, particularly where it has been desiredto obtain a grease characterized by structural sta bility at elevatedtemperatures. This property makes such greases of particular interest inthe lubrication of ball bearings and other machinery parts as well as inturbo jet engines and insteel rolling mills. Such non-soap greases,however, have not possessed rust-preventive properties equal to theearlier soap-type greases. The usual rust inhibitors generallyrecommended for use in industry have afforded little or no improvementin rust-preventive properties of the non-soap grease. Accordingly,despite the excellent high temperature characteristics of these greases,

. they have had the disadvantage of being unable to provide satisfactoryprotection against rust. Such disadvantage has, in many instances,severely limited the application of non-soap greases. Varioussuggestions and attempts have been made to overcome this deficiency,such as the addition of water repelling agents, extreme pressure agents,or anti-corrosion agents. None of the foregoing, however, have provideda non-soap grease affordingsatisfactory protection against rust.

The principal object of the present invention, accordingly, is toprovide a non-soap grease having improved rust-preventive properties.

The above and other objects which will be apparent to those skilled inthe art are achieved by the grease composition described herein. It hasbeen found, in accordance with the present invention, that a non-soapgrease having unexpected rust preventive properties may be prepared byproviding a composition containing a substantial amount of'two inorganicgrease thickening agents. Thus, the grease composition of this inventioncomprises an oleaginous liquid thickened with the combination of anorganophilic clay and an organophilic esterified product comprisingamorphous silica of specified surface area coated with alkoxy groupscontaining from 2 to 18 carbon atoms.

Each of the above thickening agents essential to the present compositionhave heretofore been separately employed in grease formulation. However,in so far as is known, grease containing these agents in combinationhave not been previously produced. It has been discoveredlthatcombination of the above inorganic thickeners in grease manufactureimparts to the resultant product rust preventive properties far superiorto rust-preventive prop erties of greases made with either of the samethickening Tee agents separately. It would appear that the combinationof thickening agents employed in the present grease results in anunpredictable synergistic action. Such unexpected action has, inaccordance with the instant invention, been found to afford a non-soapgrease having unusual rustpreventive properties.

organophilic clay, employed herein as one of the thickening agents ofthe aforesaid combination, has, as indicated above, heretofore beenemployedseparately in the production of non-soap greases. The clays usedcomprise those which have been treated with organic cationic surfaceactive agents, such as onium compounds, so as to destroy their inherenthydrophilic nature and to impart organophilic characteristics thereto.The preparation of these clays has been described in detail in theliterature, for example, in U. S. Patent 2,531,427 to Hauser. Inaccordance with the general method of preparation, clays are dispersedin a swelling medium, such as water, and treated with an onium compoundwhich causes the formation of a hydrogel wherein either absorption orion exchange reaction has occurred so that a-closely bonded compositionof the clay and oniurn radical has resulted. Clays which are useful forthe above purpose includeespecially montmorillonite clays, such asWyoming bentonite or hectorite, although other cation-exchangeable clayssuch as attapulgite, vermiculite, saponite, biotite, sepiolite, and thelike may also be used to advantage.

Typical of the greases which have been prepared with an organophilicclay are the so-called Bentone greases. Bentones are the reactionproducts of montmorillonite or, more accurately, bentonite and variousorganic cations. Bentonite' is a species of the class of minerals knownas the montmorillonites and in its natural state is a highly hydrophilichydrous aluminum silicate with a micaceous structure and anexceptionally small ultimate particle size. It customarily occurs as thesalt of a moderately strong acid in which the cation is predominantlysodium. It has heretofore been known that bentonite may be convertedinto a hydrophobic and organophilic condition by the introduction oflong chain hydrocarbon radicals into the surface of the montmorilloniteclay particles. The nature and preparation of organophilic bentoniteshas been described in detail by J. W. Jordan in the Journal of Physicaland Colloid Chemistry, volume 53, No. 2, 1949, pp. 294306. Briefly, thepreparation of an organophilic bentonite involves hydration of themontmorillonite in a very dilute dispersion to separate the unitparticles and to achieve complete removal of non-clay impurities. Thisstep is resorted to since most montmorillonite in the crude statecontains relatively large quantities of quartz which, if allowed toremain, would impart an abrasivecharacter to the resulting product. Thereactive sodium atoms of the clay particles are then replaced by organiccations and the product is washed, filtered, and dried. By proper choiceof the organic cation, the properties of the resulting modifiedmontmorillonite product can be controlled. Generally, for imparting thedesired organophilic properties, an organic ammonium compound having acarbon chain of at least 10 carbon atoms is employed. Increasing thechain length of the ammonium compound gives a product of increasingorganophilic properties. The ammonium compounds are usually converted tothe form of salts before use. Thus, organophilic bentonites have beenprepared by the reaction of bentonite withvarious aliphatic ammoniumsalts, including the salts of long chain amines and quaternary ammoniumcompounds having one or more aliphatic chains. The resulting productsare generally referred to as alkyl ammonium bentonites and are morecommonly known to the trade as Bentones. The figure following the tradename Bentone indicates the number of carbon atoms in the hydrocarbonradical or 2,847,380 Patented Aug. 12,1958 s,

radicals attached to the silicate structure of the bentonite. Forexample, Bentone 34 is a modified montmorillonite produced asabove-stated and having as cations the secondary amine radicals formedby reacting hydrated montmorillonite with technical distearyl amine.Thesemodified montmorillonite products have substantially no affinityfor water but, because of the long hydrocarbon chainscoating theparticles and the platelets of clay, they are subject to readydispersion in organic liquids.

The other essential thickening agent utilized in the grease compositionof this invention is an estersil. Estersils are organophilic solids madeby chemically reacting primary or secondary alcohols with certainsiliceous solids. For a detailed description of estersils and a methodfor'preparing the same,'reference is made to U. S. 2,657,149. Briefly,the estersils which have been employed as thickening agents in themanufacture of lubricating greases are powders or pulverized materialshaving an internal structure or substrate of inorganic siliceousmaterial having an average specific surface area of at least 25 squaremeters per gram to which- -OR groups are chemically bound, R being thehydrocarbon radical of a primary or secondary alcohol containing 2 'to18 carbon atoms; that is, a radical in which the carbon attached to theoxygen is also attached to hydrogen.

The substrates of the estersils are solid inorganic siliceous materialscontaining substantially no chemical- 1y bound organic groups prior toesterification and having silanol groups (-SiOH) on their surfaces. Theycan be mineral or synthetic in origin and thus can be amorphous silica,-insoluble metal silicates or such silicates coated with amorphoussilica. The substrate is in particulate form, the particles being ofsuper-colloidal, that is, larger than colloidal size and hence generallylarger than 150 millimicrons in at least one dimension. Such particlesmay be aggregates of much smaller particles, i. e., ultimate units whichare so firmly attached to each other that they are not readily separatedby simple stirring in a fluid medium.

In estersils to be used as thickening agents in the present greasecomposition, substrate particles are preferred in which the ultimateunits have an average diameter greater than. millimicrons or in whichthe ultimate units are below 10 millimicrons and are joined in very opennetworks to provide a large pore size. Solids having average porediameters of at least 4 millimicrons are especially preferred. Suitablesubstrates have a specific surface area of at least square meters pergram and preferably at least 200 square meters per gram. Forprecipitated amorphous silica, which is a preferred substrate, there isan optimum range of about ZOO-to 400 square meters per gram. Veryvoluminous siliceous aerogels having surface areas as great as 900square meters per gram, and preferably from 200 to 900 square meters pergram, afford very suitable substrates because of the great thickeningefficiency of estersils produced therefrom.

While various inorganic siliceous solids having properti'es asaforementioned can be used as substrates for making estersils for use inthe present grease compositions, precipitated amorphous silica ispreferred. This silica consists of coherent aggregates of non-porousultimate units in which the ultimate units are quite uniform in size andhave an average diameter greater than about 10 millimicrons or ultimateunits below 10 millimicrons diameter joined in very open networks.

The general method for preparing the estersils involves esterificationof the above-described siliceous solid with a primary or secondarymonohydric alcohol containing from 2 to 18 carborf atoms. Mixtures ofalcohols can also be used as the esterifying agent. Alcohols containingfrom 3 to 6 carbon atoms are particularly preferred since the estersilsmade therefrom are more stable toward hydrolysis than those made from9.1-

cohols of fewer carbon atoms and are more economical to use than thosemade from alcohols having a greater number of carbon atoms.

The esterified inorganic siliceous solids, i. e., the estersils, are inthe form of powders or easily pulverable particles. They are generallyexceedingly fine, light, flutfy powders, as indicated by their low bulkdensities. In particular, estersils having a bulk density not greaterthan 0.20 gram per cubic centimeter at 3 pounds per square inch and notgreater than 0.30 gram per cubic centimeter at 78 pounds per square inchare preferred. All of the above described estersils are organophilic. Inorder to make an inorganic siliceous solid organophilic, it is necessaryto react a certain minimum proportion of the surface silanol groups withan alcohol containing at least 2 carbon atoms. With most alcohols, theesterified material becomes organophilic when it contains more thanabout 80 ester groups per square millimicrons of surface of the internalstructure or substrate. The products are markedly organophilic whenthere are chemically attached more than about 100 ester groups per 100square millimicrons of substrate surface. Preferred organophilic andhydrophobic estersils are obtained by esterifying the inorganicsiliceous material to give an estersil containing at least 200 estergroups per- 100 square millimicrons of substrate surface. In the case ofthe preferred alcohols, which are those containing 3 to 6 carbon atoms,it is generally prefered to provide an estersil having at least about270 ester groups per 100 square millimicrons of substrate surface byemploying more severe reaction conditions, a greater number of alcoholmolecules; that is, 300 to 400 may be made to react per 100 squaremillimicrons of surface area of the siliceous substrate.

The oil component used incompounding present greases may be broadlydescribed as an oleaginous lubricant base, which would include theconventional mineral oils, hydrogenated fish oils, animal oils,vegetable oils, fluorocarbon oils such as the perfluorinated petroleumoils, the synthetic lubricating oils prepared by cracking andpolymerizing products of the Fischer-Tropsch process, and the like, or asynthetic oleaginous compound within the lubricating oil viscosityrange.

Typical of the latter type compounds are the liquid polyorganosiloxanes,also known as silicones. These compounds are polymers composed ofalternate silicon and oxygen atoms wherein the silicon atoms may bevariously substituted with alkyl, aryl, alkaryl, aralkyl, and cycloalkylradicals. The above siloxanes may be prepared by any appropriate method.It is contemplated that any of the various types of silicone polymersmay be employed for purposes of the present invention. Representativecompounds are the dimethyl silicone polymers, the diethyl siliconepolymers, the ethyl-phenyl silicone polymers, and the methyl-phenylsilicone polymers.

Other synthetic oleaginous compounds which may be substituted in wholeor part for the conventional mineral lubricating oils in present greasesinclude synthetic organic lubricating compounds. The choice of theparticular compounds used in the preparation of present greases willdepend in part upon the type of lubrication and the temperature rangewithin which the grease is intended to be employed. Greases preparedfrom these compounds are generally particularly adapted to specializedlubrication outside the conventional lubricating temperature ranges,such as excessively low temperature operation found in refrigerationsystems or to general purpose lubrication over a wide lubricatingtemperature range. The types of compounds which are recognized or havebeen proposed as synthetic organic lubricants include the aliphaticethers, aromatic acid esters, aliphatic monoand dicarboxylic acidesters, phosphorous acid esters, and halogenated aromatic compounds. Forthe purposes of the present invention and as illustrative squaremillimicrons of surface and characterized of the synthetic oleaginouscompounds utilized herein, those compounds falling within the categoryof aliphatic dicarboxylic acid esters are typical. The compounds withinthis particular class are the esters of such acids as sebacic, adipic,pimelic, azelaic, etc. The esters thereof are preferably the aliphaticesters and particularly the branch chain aliphatic esters. Specificrepresentative oleaginous compounds include di-iso-octyl adipate, di-2-ethyl hexyl amyl sebacate, di-sec-amyl sebacate, etc. These oleaginouscompounds, as well as the abovedescribed polyorganosiloxanes, may beused as the sole oil component of the greases or they may be blendedwith a mineral lubricating oil as desired. If desired, various additionagents may be incorporated with the oleaginous compounds to impartdesired characteristics. Thus, an extreme pressure agent may beincorporated to improve the anti-wear characteristics of the compound,or an antioxidant may be incorporated to improve the anti-oxidantproperties of the finished grease.

'The greases of the invention may be prepared by a mixing or blending ofthe combination of thickening agents and oleaginous liquid. The mixingcan be carried out in milling and mixing devices of the kind usedheretofore for producing non-soap greases wherein a single thickeningagent was employed. Ball mills, colloid mills, homogenizers, and similardevices can be used in preparing the present greases to give the desiredthorough dispersion of the combination of thickening agents in thehomogeneous liquid. The type of milling or mixing device used depends inpart upon the physical and chemical characteristics desired in thefinished grease product. Thus, a ball mill generally aifords goodresults While a high pressure homogenizer which produces high shearingforces affords maximum dispersion and thickening efficiency.

The amount of the above two thickening agents employed in formulation ofthe present grease is usually such as to thicken the base oleaginousliquid to a consistency Within the range conventionally ascribed togreases. As little as 0.5 percent by weight of the combined organophilicclay and estersil may be employed to give a semi-fluid grease.Generally, however, greater amounts of the thickening agents will beused, ordinarily from about 2 to about 30 percent by weight and moreparticularly from about 5 to about weight percent. It is important thatthe weight ratio of organophilic clay to estersil in the combinationthickening agent employed be between about 3:1 to about 1:3. It isparticularly preferred that the aforementioned weight ratio be betweenabout 1:1 and about 1:3.

The following formulae and test results embody comparative dataestablishing the exceptional rust-preventive properties of the grease ofthis invention:

Example 1 2 3 Estersil GT is an estersil marketed bv E. I. du Pont deNemours and Company consisting essentially of an amorphous silica coatedwith approximately 340 butoxy groups 213111103 mate particle size of8-10 millimicrons, a surfac area of 275-325 m."/g. and a bulk density of19-20 lb./ft..

0f the above examples, Example 2 represents a grease made. with anestersil as the only thickening agent. Example 3 represents a greasecomposition in which the only thickening agent is an organophilic clay.

Example 1 embodies the grease of the invention containing a combinationof an estersil and an organophilic clay as thickening agents. It is tobe noted that the total amount of thickening agents employed in thisexample does not exceed the amount of either of the single thickeningagents in Examples 1 and 2.

Pentaerythritol was included in Examples 1 and3 as I a high temperaturestability agent. Such material, however, is not an essential componentof the present grease composition but the inclusion thereof may be'found de--' rials familiar to those in the art, as well as water, may

also be used for such purpose and when so employed will be present inonly very minute amounts of less than 1 percent by weight. V

The above illustrative greases were made by charging to percent of themineral oil to a kettle, adding the organophilic clay thickener andpentaerythritol solution,

and heating to 240-250 F. while passing one time through a high pressurehomogenizer at 3000 5000 pounds per square inch gauge. Thereafter, theremaining oil, estersil thickener, and water, if necessary as adispersing aid, were added. The resulting mixture was then heated to280-300" F. while passing 2 to 5 times through a high pressurehomogenizer at 3000-5000 pounds per square inch gauge. In thoseinstances (Examples 2 and 3) where only a single thickening agent wasemployed, all of such agent was added initially with 60 to 70 percent ofthe mineral oil.

It is-evident from the above illustrative data that the rust-preventiveproperties of the grease of this invention are unexpectedly high.

The method of determining rust-preventive properties is a modificationof that described in paragraph No. 4.4.2.5 of Specification MIL-G-l0924.This method involves coating test panels oflow carbon steel with 0.004of the grease to be tested and exposing the grease-coated panel to asalt spray for a minimum of 100 hours. The face of the panel is thenexamined for evidence of corrosion or rusting. The panels areapproximately 3 inches long and one inch wide with slightly roundededges. Panel thickness may be from A: tol inch with the latter preferredto allow regrinding of used panels. The panels are supported at an angleof 15 degrees from the vertical and parallel to the principal directionof horizontal flow of a salt spray through an exposure chamber. The saltsolution employed is of the following composition:

The temperature in the exposure zone is maintained at approximately F.The conditions maintained in all parts of the exposure zone are suchthat a suitable receptacle placed at any point in the exposure zone willcollect from 0.5 to 3 milliliters of the aforementioned salt solutionper hour for each 80 square centimeters of horizontal collecting areabased on an average run of at least 16 hours. The test panels areexposed to the atomized salt solution for a minimum of hours or untilfailure. Specimens are examined daily for evidence of corrosion orrusting and the condition of the grease film. Rust anywhere on the 0.004inch coated surface except within M inch to /2 inch of the edgesindicates failure. The test results are reported as the time of exposurein days before the test panel shows evidence of rusting.

In addition to the essential ingredients of an oleaginous liquid and thecombination of organophilic clay and estersil thickening agents, thegreases of this invention may contain additional ingredients, forexample, antiwear agents, such as oil-soluble ureayor thioureaderivatives, e. g., urethanes, carbazides, carbazones, etc.; or rubber,polyisobutylene, polyvinyl esters, etc.; V. 1. improvers such aspolyisobutylenes having a molecular weight above about 800, volatilizedparaffin wax, unsaturated polymerized esters of fatty acids andmonohydric alcohols, etc.; oiliness agents such as stearic and v oleicacids and pour point depressors such as an alkylated naphthalene.

The greases described herein, if desired, may be stabilized againstoxidation by the addition of a minor amount of an oxidation inhibitor.Suitable anti-oxidants efiective with grease compositions of the presentinvention are: N-alkyl paraphenylenediamine and condensed polynucleararomatic monoamines. Such inhibitors are N- butyl paraphenylenediamine,N-N-dibutyl paraphenylenediamine, etc. Also effective as oxidationinhibitors are alpha or betanaphthylamine, phenyl-alpha orbetanaphthylamine, alpha-alpha, beta-beta, oralpha-betadinaphthylarnine, diphenylamine, tetramethyldiamino,diphenylmethane, petroleum alkyl phenols, and 2,4ditertiarybutyl-6.methyl phenol.

The grease compositions of this invention may also contain extremepressure agents. Such suitable agents comprise esters ofphosphorous'acids such as triaryl, alkylhydroxy, aryl, or aralkylphosphates, thiophosphates or phosphites, etc.; neutral aromatic sulfurcompounds such as diaryl sulfides and polysulfides, e. g., diphenylsulfide, dicresyl sulfide, dibenzyl sulfide, methyl butyl diphenylsulfide, etc.; diphenyl selenide and diselenide; sulfurized fatty oilsor esters of fatty acids and monohydric alcohols, e. g., sperm oil,jojoba oil, etc., in which the sulfur is tightly bound; sulfurizedlong-chain olefins obtained by dehydrogenating or cracking of wax;sulfurized phosphorized fatty oils, acids, esters and ketones,phosphorous acid esters having sulfurized organic radicals, such asesters of phosphoric or phosphorous acids with hydroxy fatty acids,chlorinated hydrocarbons such as chlorinated paraffins, aromatichydrocarbons, terpenes, mineral lubricating oil, etc., or chlorinatedesters of fatty acids containing the chlorine in position other thanalpha position.

It is to be understood that the above description is merely illustrativeof preferred embodiments of the invention, of which many variations maybe made within the scope of the following claims by those skilled in theart without departing from the spirit thereof.

I claim:

1. A grease composition consisting essentially of an oleaginouslubricant liquid and a sufiicient amount to thicken said liquid to agrease consistency of a thickening agent consisting essentially of amixture of an organophilic bentonite in which the exchangeable inorganiccation has been replaced by an organic ammonium base having a carbonchain of at least l carbon atoms and an organophilic estersil comprisinga supercolloidal substrate coated with -OR groups, the substrate havinga surface of silica and having a specific surface area of from 25 to 900square meters per gram, the coating of --OR groups being chemicallybound to said silica, R being a hydrocarbon radical of from 2 to l8carbon atoms, wherein the carbon atom attached to oxygen is alsoattached to hydrogen in which the weight ratio of said bentonite to saidestersil is between about 3:1 to about 1:3.

2. A grease composition consisting essentially of an oleaginouslubricant liquid and a sufiicient amount to thicken said liquid to agrease consistency of a thickening agent consisting essentially of amixture of an organo philic bentonite in which the exchangeableinorganic cation has been replaced by an organic ammonium base having acarbon chain of at last 10 carbon atoms and an organophilic estersilcomprising a supercolloidal substrate coated with OR groups, thesubstrate having a surface of silica and having a specific surface areaof from 25 to 900 square meters per gram. the coating of OR groups beingchemically bound to said silica, R being a hydrocarbon radical of from 2to 18 carbon atoms, wherein the carbon atom attached to oxygen is alsoattached to hydrogen in which the weight ratio of said bentonite to saidestersil is between about 1:1 to about 1:3.

major amount of a mineral lubricating oil and a minor" amount,sufiicient to thicken said oil'to a grease consisteucy, of a mixture ofan organophilic bentonite in which the inorganic cation has beenreplaced by an organic ammonium base having a carbon chain of at least10 carbon atoms and an organophilic estersil comprising a supercolloidalsubstrate coated with OR groups, the Substrate having a surface ofsilica and having a surface area of from 25 to 900 square meters pergram. the coating of ,OR groups being chemically bound to said silica, Rbeing a hydrocarbon radical of from 2 to 18 carbon atoms, wherein thecarbon atom attached to oxygen is also attached to hydrogen, the weightratio of the former'to the latter component in said mixture beingbetween about 3 :l and about 1 :3.

5. A lubricating composition comprising a major amount of a minerallubricating oil and a minor amount sufiicient to thicken said oil to agrease consistency of a mixture of an organophilic bentonite in whichthe inorganic cation has been replaced by an organic ammonium basehaving a carbon chain of at least 10 carbon atoms and an organophilicestersil comprising a supercolloidal substrate coated with OR groups,the substrate having a surface of silica and having a surface area offrom 25 to 900 square meters per gram, the coating of OR groups beingchemically bound to said silica, R

being a hydrocarbon radical of from 2 to 18 carbon atoms, wherein thecarbon atom attached to oxygen is also attached to hydrogen, the weightratio of the former to the latter component in said mixture beingbetween about 1:1 and about 1:3.

6. A grease composition comprising an oleaginous lubricant liquid and asufficient amount to thicken said liquid to a grease consistency of athickening agent consisting essentially of a mixture of an organophilicbentonite in which the exchangeable inorganic cation has been replacedby an organic ammonium base having a carbon chain of at least 10 carbonatoms and an organophilic estersil comprising a supercolloidal substrateof amorphous silica coated with alkoxy groups, the substrate having anaverage pore diameter of at least 4 millimicrons and a specific surfacearea of from 200 to 900 square meters per gram and the alkyl radical ofthe alkoxy group in the coating being a hydrocarbon radical of from 2 to18 carbon atoms, wherein the carbon attached to oxygen is also attachedto hydrogen, the weight ratio of said organophilic bentonite to saidorganphilic estersil being between 3:l and 1:3.

7. A grease composition comprising a mineral lubricating oil thickenedwith from about 5 to about 20 weight per cent of a gelling agentconsisting essentially of: (1) an organophilic bentonite having theexchangeable inorganic cation thereof replaced by an organic ammoniumbase having a carbon chain of at least 10 carbon atoms, and (2) anorganophilic estersil comprising a supercolloidal substrate coated withalkoxy groups, the substrate having a surface of silica and having aspecific surface area of from 25 to 900 square meters per gram, therebeing in the alkoxy group coating chemically bound to said silica, atleast alkoxy groups per 100 square millimicrons of substrate surfacearea, the alkyl radical of the alkoxy group being a hydrocarbon of from2 to 18 carbon atoms, wherein the carbon attached to oxygen is alsoattached to hydrogen, the weight ratio of said organophilic bentonite tosaid organophilic estersil in said mixture being between about 1:1 andabout 1:3.

8. A grease composition comprising an oleaginous lubricant liquid and agrease-forming amount of a mixture of an organophilic bentonite in whichthe exchangeable inorganic cation has been replaced by an organicasa'nsee ammonium base having a carbon chain of at least 10 carbon atomsand an organophilie estersil comprising a supcrcolloidal siliceoussubstrate coated with -OR groups, the substrate having a surface ofsilica and having a specific surface area of from 25 to 900 squaremeters per gram, the coating of --OR groups being chemically bound tosaid silica and R being a hydrocarbon radical of from 3 to 6 carbonatoms, wherein the carbon atom attached to oxygen is also attached tohydrogen, the weight ratio of said organophilic bentonite to saidorganophilic estersil being between about 1:1 and about 1:3.

9. A grease composition comprising a mineral lubricating oil and fromabout 2 to about 30 percent by weight of a mixture consistingessentially of an organophilic bentonite in which the exchangeableinorganic cation has been replaced by an organic ammonium base having acarbon chain of at least 10 carbon atoms and an organophilic est'ersilcomprising a supercolloidal substrata of amorphous silica coated with--OR groups, the substrate having a specific surface area of from 25 to900 square meters per gram, the coating of -OR groups being chemicallybound to said silica and R being a hydrocarbon radical of from 2 to 18carbon atoms, wherein the carbon atom attached to oxygen is alsoattached to hydrogemthe weight ratio of said organophilic bentonite tosaid organophilic estersil in said mixture being between about 3:1 and1:3.

References Cited in the file of this patent UNITED STATES PATENTS

1. A GREASE COMPOSITION CONSISTING ESSENTIALLY OF AN OLEAGINOUSLUBRICANT LIQUID AND A SUFFICIENT AMOUNT TO THICKEN SAID LIQUID TO AGREASE CONSISTENCY OF A THICKENING AGENT CONSISTING ESSENTIALLY OF AMIXTURE OF AN ORGANOPHILIC BENTONITE IN WHICH THE EXCHANGEABLE INORGANICCATION HAS BEEN REPLACED BY AN ORGANIC AMMONIUM BASE HAVING A CARBONCHAIN OF AT LEAST 10 CARBON ATOMS AND AN ORGANOPHILIC ESTERSILCOMPRISING A SUPERCOLLOIDAL SUBSTATE COATED WITH -OR GROUPS, THESUBSTRATE HAVING A SURFACE OF SILICA AND HAVING A SPECIFIC SURFACE AREAOF FROM 25 TO 900 SQUARE METERS PER GRAM, THE COATING OF -OR GROUPSBEING CHEMICALLY BOUND TO SAID SILICA, R BEING A HYDROCARBON RADICAL OFFROM 2 TO 18 CARBON ATOMS, WHEREIN THE CARBON ATOM ATTACHED TO OXYGEN ISALSO ATTACHED TO HYDROGEN IN WHICH THE WEIGHT RATIO OF SAID BENTONITE TOSAID ESTERSIL IS BETWEEN ABOUT 3:1 TO ABOUT 1:3.